A general protocol to prepare surface molecularly imprinted polymer core–shell superparamagnetic Fe₃O₄ nanoparticles (Fe₃O₄@MIP SPNPs), using a surface-mediated RAFT polymerization approach, is described. Cholesterol-imprinted Fe₃O₄@MIP SPNPs were obtained by oleic acid-stabilized Fe₃O₄ nanoparticles with a trithiocarbonate agent and subsequently by polymerizing thin molecularly imprinted layers composed of dimethylacrylamide and N,N′-methylene(bis)acrylamide units. The surface-mediated RAFT polymerization approach allows the synthesis of ∼20 nm hybrid composite particles with a ∼6 nm MIP shell, exhibiting superparamagnetic properties (saturation magnetization = 35.4 emu g⁻¹) and specific molecular recognition of cholesterol. The Fe₃O₄@MIP SPNPs show the capability of rapid enriching and separating cholesterol (∼3.1% in weight) and are renewable and cyclically exploited due to their monodispersive and superparamagnetic features. Moreover, under optimal conditions, the Fe₃O₄@MIP SPNP recoveries of spiked human serum, milk, yolk and beef were 91.6%, 93.6%, 92.4% and 91.2%, respectively. Finally, the method of molecular imprinting on superparamagnetic particles can be extended to a wide range of applications for cell sorting, biomolecule enrichment and separation, and drug delivery.

Molecularly imprinted polymer (MIP) films on silicon wafers were prepared by surface-initiated atom transfer polymerization (ATRP). 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate were used as the functional monomer and the cross-linking agent, respectively. Myoglobin (Mb) was selected as the template molecule to form the MIP films. Various characterization techniques including ellipsometry, contact-angle goniometer, atomic force microscopy, grazing angle-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, were used to characterize the films. Ellipsometry was also used to quantify and compare the binding capacity of the MIP and nonimprinted polymer (NIP) films. The MIP films exhibited higher rebinding capacity than the NIP films at all solution concentrations of Mb. A selectivity coefficient of 3.15 was achieved for the MIP films prepared against the Mb template molecule.

A novel poly( N -(2-hydroxypropyl) methacrylamide) [poly(HPMA)] brush with a moderate density polymer brush (0.52 chains per nm ² ) was synthesized by an interface-mediated RAFT polymerization.